1. Field of the Invention
This invention relates generally to refrigerating apparatus and more particularly, it relates to an evaporator feed and control system which provides a high level of stability over a wide range of varying load conditions. This invention has specific applications with controlled displacement compressors in which a minor stroking is maintained at minimum capacity.
2. Description of the Prior Art
In U.S. Pat. No. 2,806,674 issued to G. L. Biehn on Sept. 17, 1957, there is disclosed a heat pump having an indoor air coil formed of three vertical rows of finned tubes and an additional vertical row of finned tubes located upstream thereof.
In U.S. Pat. No. 2,707,868 issued to W. Goodman on May 10, 1955, there is disclosed a refrigeration system having a mixing valve which is responsive to the superheat of the refrigerant in the return conduit for feeding a mixture of liquid and gaseous refrigerant to a supply header in various proportions in accordance with the superheat.
It is generally known in the refrigeration art to pass liquid refrigerant through an expansion valve or a similar device and into a distributing header of an evaporator to effect the desired cooling of air or other fluid which is passed over the surfaces of the evaporator. While desired operation of the evaporator is usually reached during its full or rated capacity condition, it has been encountered heretofore in the industry that where an evaporator is being utilized at a low or partial level of its full capacity even distribution of liquid refrigerant through the plurality of tubes forming the evaporator is very difficult to maintain. It would, therefore, be desirable to provide an evaporator system which will supply even or stable distribution of liquid refrigerant to the evaporating tubes during a wide range of partial load conditions as well as at full load or capacity.
In the usual refrigeration systems, a mixture of liquid refrigerant and a relatively small amount of oil circulates throughout the system. Since the oil comes from the compressor crankcase, it must be returned thereto so as to prevent the depletion of the supply in the crankcase thereby causing compressor failure. It would be thus desirable to provide a refrigeration system having an evaporator wherein the unevaporated oil will be returned to the compressor along with the refrigerant vapor leaving the evaporator.
Since it has been recognized in practice that the load on the evaporator may vary considerably, it would also be desirable to vary the supply of refrigerant flowing within the evaporator in response to such variations. Thus, there is provided in the present invention an evaporator having valve means connected at its outlet to bypass a portion or all of the refrigerant to the compressor when a low or zero capacity is required.